Thursday, 29 May 2014

Jellyfish are different, at least some of them. The comb jellyfish
“Pacific sea gooseberry”
(Pleurobrachia bachei) hunts for food. It is a predator, paddling through the sea, and
grasping its prey with sticky tentacles.

Pacific sea gooseberry(from Wikipedia Commons)

Recent analysis of the Pacific sea
gooseberry revealed a fascinating detail, making them much of an
alien [1]. Their nervous system miss the habitual set of components that
are found in most other animals. The chemical signals
(neurotransmitter) of the Pacific sea gooseberry, which make the nerves work are different. The Pacific sea gooseberry does not use the set of chemical signals that we know from most animals.

Without question, the Pacific sea gooseberry has a fully
developed nervous system. It consist of a network with a ring of nerves
around the mouth. The nervous systems senses light, detects prey and
coordinates moves of muscles. However, the nervous system performing
these operations is using different chemical signals. That is less
than a detail. It indicates that nervous systems evolved on Earth
twice, at least. The deciphered gene code of the Pacific sea
gooseberry shows this.

Other differences between Pacific sea gooseberry and
other animals are found for immune and development genes, and
respectively for the related physiological processes.

Whether
comb jellies descend from ancient organisms that lived 580
million years ago (in the Ediacaran [*] ), as some speculate, is a provocative hypothesis. If
that is the case, then the
Pacific sea gooseberry
may trace that ancient world to present times and indicate how
complex this ancient world was already. Ecosystems with prey-predator
relationship existing more than half a billion years ago!

A comb jellyfish
(from Wikipedia Commons)

A
less precocious hypothesis would be that the evolution of
Pacific sea gooseberry included the replacement of the chemical
signals that we know to be common in nearly all animals.

What
should be noted, beyond any speculation, that the sea is full of
treasures. Many we only do not know; one more was discovered recently.

Understanding that nervous systems, immune systems or development
process can be constructed from different building blocks is deep
insight with possibly far-reaching consequences,
be it for regenerative
medicine or synthetic biology [3].

Comb jellyfish [**] are classified as a sister group to
jellyfish and sea anemones. This kind of animals are ancient and
lived in the ocean since very long time, even if the modern species
evolved more recently. These animals have in common that the
distinction between head and rears does not apply to them as it
applies for slugs, fish and humans. This feature makes them simpler
and they are put at the bottom of the tree of life, comb jellies
among them. Thus it is useful to assume that similar functions
evolved several times along parallel paths.

Martin.Mundusmaris@gmail.com

info@mundusmaris.org

[*]
The
Ediacaran (635 - 542 million years) is the geological period
preceding
the CambrianPeriod.
The Ediacaran biota have little resemblance to modern lifeforms and
include the oldest organismswith
tissues; hard-shelled animals had yet to evolve.

Saturday, 10 May 2014

To recall, sea-birds confuse
small bits of plastic with food. They swallow the bits of plastic and
it kills them. [a] To recall, abandoned fishing gear entangles fish,
turtles and marine mammals, and its kills them. Floating plastic
bags do the same. And so on, but that is not the end of the story
[1].

The NOAA Marine Debris Program funds projects to remove derelict fishing nets and other debris from marine waters, where they can entangle marine life. (NOAA)

Each
year some
6.4 million tonnes of litter are entering the oceans, or about one
kilogram for each human being. Most litter stems from cities. “The
world's cities currently generate around 1.3 billion tonnes of
municipal solid waste a year, or 1.2 kilogram per city-dweller per
day.” [b Thus, the litter discharged into the sea corresponds to
about 4-5% of the municipal solid waste produced in the cities of the
world. In that sense its a small part of waste produced by the nine
billion humans, but as any dumping it causes problems.

More
generally, marine
litter is defined as ‘‘any persistent, manufactured or processed
solid material discarded, disposed of or abandoned in the marine and
coastal environment." Persistent littering the sea likely has
started with disposing “clinker” from steamships and currently
has found its peak with “plastic”.

Clinker,
the residue of burnt coal, was commonly dumped from steamships well
into the 20th century. In the Mediterranean Sea, its occurrence on
the deep sea-floor has been shown to coincide with such shipping
routes.

Currently,
the most abundant marine litter is plastic. Only part of the plastic
items float at the sea surface or close to it. Two third of the
plastic sinks to the bottom of the sea when converted by fouling
organisms. Therefore plastic accumulation on the seabed is more
abundant than in the open sea. Thus, below the floating garbage is an
even bigger garbage dump at the sea bottom.

Litter
is present in all marine habitats, from beaches to the most remote
points in the oceans, such as the Midway Islands in the Pacific [a.
The
particular distribution
and accumulation of litter in the ocean is influenced by water
movements, bottom morphology and economic activities.

On
the global scale, the ocean currents sweep the litter to the centre
of the ocean-gyres where it accumulates, called the big garbage
patch. On the local scale, litter is washed upon the beach. On the
hidden scale, litters is channelled to the deep sea. Marine litters
accumulates in particular high densities in submarine canyons.

Submarine
canyons act as passages for litter transport from continental shelves
into deeper waters. Submarine canyons are areas where organic debris
accumulates. The debris is food for bottom-dwelling fauna and
suspension-feeding invertebrates. They are abundant in submarine
canyons. The accumulation of plastics in submarine canyons likely has
a detrimental effects on theses deep-sea organisms.

A survey [2] of European seas published in April 2014, confirmed again that marine litter is found everywhere, from the beach down to the deep sea. The survey uses standardized methods to categorize the litter and to quantify its abundance. Most common litter items included, non-surprisingly, plastic bags, glass bottles and abandoned fishing lines and nets:

Plastic
represented 41% of the litter items in European seas, whilst
abandoned fishing gear accounted for 34% of the total. Clinker,
glass and metal are least common. Density and composition of litter
in European seas is comparable to what has found in other parts of
the world ocean.

Litter
density in submarine canyons reached an average of 12.2 – 6,4
items per ten-thousand square meters, or the double of the litter density found elsewhere.

A litter density of 12.2 – 6,4 items per ten-thousand square meters means to find about 10 items of
litter on a surface wide as a football field!

A list of locations
with highest litter densities in European waters includes for
example the Lisbon Canyon in continental shelf of Portugal or the
Blanes Canyon in the continental shelf of the Mediterranean sea of
Spain. Theses canyons were formed when the sea-level was much lower
than today.

Litter is a serious risk for
the marine environment. Entanglement in abandoned fishing gear is a
serious threat for birds, turtles and marine mammals, it is also
causing high mortality of fish through ‘‘ghost fishing''. Beyond
other threats, plastic is a source of toxic chemicals that is lethal
to marine fauna.

from: http://manuals.deere.com/

The degradation of plastics
generates micro-plastics that are ingested by organisms, leading to
contaminants across trophic levels up to the fish [3] that we may
eat. So plastic debris may return to their source, finally.

About Me

My professional education is physical oceanographer and physical limnology (PhD). I worked on marine and freshwater environments. Since two decades I work in the management of the European research programmes.
And for the lawyers, this blog represents my views only and not those of my employer.